What amino acids are preferred in alpha-helices?

[Seyed A Alavizadeh]

I am curious to know if there are particular amino acids that are 
preferred for the formation of alpha-helices. Can someone tell me which 
ones these are?

thanks.

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S. Ali Alavizadeh                              Department of Biology
alavizad at mail.sas.upenn.edu               University of Pennsylvania
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